After a great chat on the design with Glenderg the other day, I went back to the drawing board with the lower half of the plan.
So, here's one version of the 'new' bottom left.
The junction bottom right comes off the 'stairwell viaduct' and splits the track into a high level through station and a gentle 2% incline down to the under-terminus-fiddle roads.
The radius of the curve is just a little more than 6 feet, and the space between the points for trains to stop is ample for a 9 foot train.... The double line down the incline will provide a nice sweeping scenic feature too, which can sit in a cutting at the bottom near the terminus, before entering an urban tunnel under the terminus board itself.
The left hand corner then provides scenic space for a small town scene, maybe the archetypal bus depot, etc
(ps: the cement terminus will be re-added in front of this again, shortly